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   /*
    * Copyright 2014 The Netty Project
    *
    * The Netty Project licenses this file to you under the Apache License, version 2.0 (the
    * "License"); you may not use this file except in compliance with the License. You may obtain a
    * copy of the License at:
    *
    * https://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software distributed under the License
   * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
   * or implied. See the License for the specific language governing permissions and limitations under
   * the License.
   */
  package io.netty.handler.codec.http2;
  
  import io.netty.buffer.ByteBuf;
  import io.netty.channel.ChannelHandler;
  import io.netty.channel.ChannelHandlerContext;
  import io.netty.handler.codec.base64.Base64;
  import io.netty.handler.codec.http.FullHttpResponse;
  import io.netty.handler.codec.http.HttpClientUpgradeHandler;
  import io.netty.handler.codec.http.HttpRequest;
  import io.netty.util.collection.CharObjectMap;
  import io.netty.util.internal.UnstableApi;
  
  import java.util.Collection;
  import java.util.Collections;
  import java.util.List;
  
  import static io.netty.handler.codec.base64.Base64Dialect.URL_SAFE;
  import static io.netty.handler.codec.http2.Http2CodecUtil.HTTP_UPGRADE_PROTOCOL_NAME;
  import static io.netty.handler.codec.http2.Http2CodecUtil.HTTP_UPGRADE_SETTINGS_HEADER;
  import static io.netty.handler.codec.http2.Http2CodecUtil.SETTING_ENTRY_LENGTH;
  import static io.netty.util.CharsetUtil.UTF_8;
  import static io.netty.util.ReferenceCountUtil.release;
  import static io.netty.util.internal.ObjectUtil.checkNotNull;
  
  /**
   * Client-side cleartext upgrade codec from HTTP to HTTP/2.
   */
  @UnstableApi
  public class Http2ClientUpgradeCodec implements HttpClientUpgradeHandler.UpgradeCodec {
  
      private static final List<CharSequence> UPGRADE_HEADERS = Collections.singletonList(HTTP_UPGRADE_SETTINGS_HEADER);
  
      private final String handlerName;
      private final Http2ConnectionHandler connectionHandler;
      private final ChannelHandler upgradeToHandler;
      private final ChannelHandler http2MultiplexHandler;
  
      public Http2ClientUpgradeCodec(Http2FrameCodec frameCodec, ChannelHandler upgradeToHandler) {
          this(null, frameCodec, upgradeToHandler);
      }
  
      public Http2ClientUpgradeCodec(String handlerName, Http2FrameCodec frameCodec, ChannelHandler upgradeToHandler) {
          this(handlerName, (Http2ConnectionHandler) frameCodec, upgradeToHandler, null);
      }
  
      /**
       * Creates the codec using a default name for the connection handler when adding to the
       * pipeline.
       *
       * @param connectionHandler the HTTP/2 connection handler
       */
      public Http2ClientUpgradeCodec(Http2ConnectionHandler connectionHandler) {
          this((String) null, connectionHandler);
      }
  
      /**
       * Creates the codec using a default name for the connection handler when adding to the
       * pipeline.
       *
       * @param connectionHandler the HTTP/2 connection handler
       * @param http2MultiplexHandler the Http2 Multiplexer handler to work with Http2FrameCodec
       */
      public Http2ClientUpgradeCodec(Http2ConnectionHandler connectionHandler,
          Http2MultiplexHandler http2MultiplexHandler) {
          this((String) null, connectionHandler, http2MultiplexHandler);
      }
  
      /**
       * Creates the codec providing an upgrade to the given handler for HTTP/2.
       *
       * @param handlerName the name of the HTTP/2 connection handler to be used in the pipeline,
       *                    or {@code null} to auto-generate the name
       * @param connectionHandler the HTTP/2 connection handler
       */
      public Http2ClientUpgradeCodec(String handlerName, Http2ConnectionHandler connectionHandler) {
          this(handlerName, connectionHandler, connectionHandler, null);
      }
  
      /**
       * Creates the codec providing an upgrade to the given handler for HTTP/2.
       *
       * @param handlerName the name of the HTTP/2 connection handler to be used in the pipeline,
       *                    or {@code null} to auto-generate the name
       * @param connectionHandler the HTTP/2 connection handler
       */
     public Http2ClientUpgradeCodec(String handlerName, Http2ConnectionHandler connectionHandler,
         Http2MultiplexHandler http2MultiplexHandler) {
         this(handlerName, connectionHandler, connectionHandler, http2MultiplexHandler);
     }
 
     private Http2ClientUpgradeCodec(String handlerName, Http2ConnectionHandler connectionHandler, ChannelHandler
         upgradeToHandler, Http2MultiplexHandler http2MultiplexHandler) {
         this.handlerName = handlerName;
         this.connectionHandler = checkNotNull(connectionHandler, "connectionHandler");
         this.upgradeToHandler = checkNotNull(upgradeToHandler, "upgradeToHandler");
         this.http2MultiplexHandler = http2MultiplexHandler;
     }
 
     @Override
     public CharSequence protocol() {
         return HTTP_UPGRADE_PROTOCOL_NAME;
     }
 
     @Override
     public Collection<CharSequence> setUpgradeHeaders(ChannelHandlerContext ctx,
         HttpRequest upgradeRequest) {
         CharSequence settingsValue = getSettingsHeaderValue(ctx);
         upgradeRequest.headers().set(HTTP_UPGRADE_SETTINGS_HEADER, settingsValue);
         return UPGRADE_HEADERS;
     }
 
     @Override
     public void upgradeTo(ChannelHandlerContext ctx, FullHttpResponse upgradeResponse)
         throws Exception {
         try {
             // Add the handler to the pipeline.
             ctx.pipeline().addAfter(ctx.name(), handlerName, upgradeToHandler);
 
             // Add the Http2 Multiplex handler as this handler handle events produced by the connectionHandler.
             // See https://github.com/netty/netty/issues/9495
             if (http2MultiplexHandler != null) {
                 final String name = ctx.pipeline().context(connectionHandler).name();
                 ctx.pipeline().addAfter(name, null, http2MultiplexHandler);
             }
 
             // Reserve local stream 1 for the response.
             connectionHandler.onHttpClientUpgrade();
         } catch (Http2Exception e) {
             ctx.fireExceptionCaught(e);
             ctx.close();
         }
     }
 
     /**
      * Converts the current settings for the handler to the Base64-encoded representation used in
      * the HTTP2-Settings upgrade header.
      */
     private CharSequence getSettingsHeaderValue(ChannelHandlerContext ctx) {
         ByteBuf buf = null;
         ByteBuf encodedBuf = null;
         try {
             // Get the local settings for the handler.
             Http2Settings settings = connectionHandler.decoder().localSettings();
 
             // Serialize the payload of the SETTINGS frame.
             int payloadLength = SETTING_ENTRY_LENGTH * settings.size();
             buf = ctx.alloc().buffer(payloadLength);
             for (CharObjectMap.PrimitiveEntry<Long> entry : settings.entries()) {
                 buf.writeChar(entry.key());
                 buf.writeInt(entry.value().intValue());
             }
 
             // Base64 encode the payload and then convert to a string for the header.
             encodedBuf = Base64.encode(buf, URL_SAFE);
             return encodedBuf.toString(UTF_8);
         } finally {
             release(buf);
             release(encodedBuf);
         }
     }
 }